1. Field of the Invention
The present invention relates to method and apparatus for forming holes into a printed circuit board by using an energy beam such as a laser beam or the like.
Further, the invention relates to a method of checking a penetrating state of a through hole in the case where a through hole is formed into a circuit pattern portion of a printed circuit board by using an energy beam such as a laser beam and where the beam is irradiated from the surface of the printed circuit board and the material constructing the printed circuit board is fused and discharged and penetrated to the back surface, thereby forming a through hole.
2. Related Background Art
Hitherto, when through holes are formed into a printed circuit board, a mechanical working method using a drill is used to form a hole. Particularly, as a diameter of a through hole to be worked decreases, a hole forming process is executed by using an expensive ultrahard drill having a high physical rigidity.
FIGS. 7A and 7B are diagrams showing a conventional hole forming process using a drill.
FIG. 7A is a cross sectional view of a hole showing a state in which a hole was formed into a two-sided epoxy board 6 by using a drill 9. According to this method, as shown in the diagram, random concave and convex portions are formed on the wall surface of the hole or a deviation is caused between the opening positions of the upper and lower surfaces due to the shooting of the drill. As shown in FIG. 7B, if a conductor is formed in such a through hole, the conductor cannot be uniformly formed, resulting in a cause of the occurrence of a defective conduction.